1. Field of the Invention
The present invention relates to a recording-medium-conveying device that conveys a recording medium and performs skew correction, and to a recording apparatus including the recording-medium-conveying device.
2. Description of the Related Art
In recording apparatuses in which images are formed by recording units while recording media are conveyed, various measures have been taken for improving the accuracy in conveyance of the recording media. If a recording medium is gradually deviates from a reference position while being conveyed, an image may not be formed correctly on the recording medium, resulting in image failure due to deviation in print position. To solve such a problem, some measures have been taken in the related art. An exemplary measure will be described below.
In Japanese Patent Laid-Open No. 62-215449, a recording medium is nipped between and is conveyed by a first roller made of an elastic material and a second roller made of a rigid material and facing the first roller. The contact pressure produced at the nip between the first and second rollers is adjustable in such a manner as to vary with the position in the recording-medium-width direction. According to such a configuration, when the contact pressure on one side in the recording-medium-width direction is increased, the first roller, which is an elastic member, is deformed, whereby the radius of the roller that conveys the recording medium is reduced. Therefore, the length of conveyance on the side where the contact pressure has been increased is reduced. Thus, any skew of the recording medium is corrected.
In recent years, however, it has become popular that printing is performed on glossy photo paper so that an image having as high quality as photographic quality can be obtained. Particularly, inkjet recording apparatuses have been desired to be capable of recording dots of microscopic sizes at higher density and with higher definition. Under such circumstances, the accuracy in conveyance of a recording medium needs to be improved dramatically, and the recording medium needs to be treated more carefully when printing is performed than in related-art cases. In this respect, mechanisms and control methods in the related art have faced limits.
Specifically, techniques in the related art have problems described below.
Since the print surface of glossy photo paper is highly specular and vulnerable, if the contact pressure produced at the nip between a pair of conveying rollers is increased, the print surface may have scratches and/or marks due to the increased contact pressure, deteriorating the print quality.
Moreover, since the roller for conveying the recording medium is deformed, the diameter of the roller may change during conveyance, resulting in unstable conveyance accuracy. Even a slight change in the diameter of the roller may lead to a non-negligible error in terms of accuracy in the conveyance of recording media on which high-definition images are to be formed as demanded in recent years.
In some cases, to drive the conveying roller with higher accuracy, a rigid roller made of a metal shaft coated with ceramic is employed. Such a rigid roller, however, is not applicable to the technique of correcting a skew by deforming a roller.